Evaporative loses of hydrocarbons from motor fuel tanks contribute significantly to the unburned hydrocarbons emitted to the atmosphere. In 1991, the Environmental Protection Agency plans to require each vehicle manufacturer to provide an on-board method of recovering fuel vapors during a fuel refilling process. For safety reasons, such method must also provide for closing the vapor recovery line after completing the refueling process to prevent fuel from escaping during a collision or rollover. Automobile manufacturers desire, of course, to effect these ends with minimum changes to the vehicle and minimum changes to the customary refueling sequence.